Metamerism is the change in color difference between a pair of samples. Metamerism occurs because each type of cone in the eye responds to the cumulative energy from a broad range of wavelengths so that different combinations of light across all wavelengths can produce an equivalent receptor response and the same tristimulus values or color sensation. Colors that match are called metamers. Metameric matches made between two light sources provide the trichromatic basis of colorimetry. The magnitude of metamerism can be measured by a change in ΔE CMC for a sample pair between two illuminants. A metameric pair could have a ΔE CMC=0 in a first light and a high ΔE CMC in a second light. Metameric pairs should match under a reference condition but mismatch under a test condition. The degree of metamerism is a measure of the degree of mismatch under the test condition.
A seasoned color expert (human) may be able to visually determine which spot colors are best to use on a given marking device from a metamerism perspective. However, the average user/customer of document reproduction devices is not likely to have the experience and visual acuity to select colors best viewed under different lighting sources. Having precise metrics, relative to metamerism, for a given spot color at the start of a print/copy job greatly benefits system operators in their print/copy job environments.
Accordingly, what is needed in this art are increasingly sophisticated systems and methods for generating a spectral matching guide based upon a metameric metric calculated for a library of spot colors available on a digital front end (DFE) of a print device for use in spot color applications in a print/copy job environment.